Joe Cassano, right, with his Fire Commissioner father Salvatore Cassano.

The first-responder son of city Fire Commissioner Salvatore Cassano resigned today after The Post revealed his history of racist, anti-semitic writings.

Mayor Bloomberg said EMT Joe Cassano has stepped down from job after his “offensive” online rants were exposed.

“I found the messages offensive,” Bloomberg said.

“It is my understanding that he has chosen to resign from the fire department. I think that’s the appropriate thing and I’ll leave it there.”

Salvatore Cassano apologized for his son’s rants.

“I am extremely disappointed in the comments posted online by my son Joseph, which do not reflect the values – including a respect for all people – that are held by me, my family and the FDNY,” Commissioner Cassano said.

“I have worked hard for many years, as have so many people in the agency, to make the FDNY more diverse and inclusive. There is no place – and I have no tolerance – for statements that would harm the good reputation we enjoy due to our honorable service to all New Yorkers.”

The disappointed dad said he still loves his son, despite this ugly incident.

“As a parent, this is very painful for me, but I believe my son has made the right decision [to resign],” Salvatore Cassano said. “I love him very much and, with the support and love of our entire family, we will get through this together.”

The Post reported this morning Joe Cassano’s long record of using Twitter to complain about his EMT job. On Feb. 3, Cassano tweeted: “Getting sick of picking up all these obama lovers and taking them to the hospital because their medicare pays for an ambulance and not a cab.”

Cassano even once tweeted: “I like jews about as much as hiter.”

The young EMT apparently isn’t much of a fan of President Obama’s health-care policies.

Posted from his Twitter account, @jcassano15, he tweeted: “Gotta love people with the iPhone 5 and brand new Jordan’s whip out their benefits card #f–kobama #ipaidforyourstuff.”

In another tweet, he Cassano complained, “Got kicked in the shin by a drunk and had to carry a 275 pound guy down 5 flights of stairs . . . my job is the worst #yearandahalftogo.”

Before last November’s election, Joseph Cassano vowed to “move to Scotland” if Obama were re-elected.

On Martin Luther King Jr. Day, he posted, “MLK could go kick rocks for all I care, but thanks for the time and a half today.”

Joseph and two other scions of FDNY brass are among 100 new hires at the EMS — where about 40 percent of personnel are minorities.

EMS members get first crack at joining the FDNY as firefighters under new federal diversity rules that put them ahead of “open competitive” applicants to the Fire Academy.

Those rules were adopted after federal Judge Nicholas Garaufis found that the FDNY had for years discriminated against minorities.

As The Post exclusively reported yesterday, critics say the EMS gig allows Cassano and his well-connected co-workers a shortcut into the FDNY.

The young Cassano made it clear earlier this month that he wants to join the FDNY, tweeting, “I hate ems” and, “Everybody wanna be a firefighter, but don’t nobody wanna be a damn EMT.”

He has no love for the NYPD, either, tweeting in September: “U couldn’t pay me enough to be a cop, there’s absolutely no direction in that department and I’m very glad I’m going the other way.”

Early this morning, Joseph Cassano released a statement through an FDNY spokesman that said, “I regret posting some comments that were offensive, especially since I enjoy my job and treat every patient with great care and respect.”

Cassano’s commissioner father said today, “My son said he regrets those comments. I think we all regret it because that’s not my son.”

The boorish tweets started before Joseph was even hired by the city.

“News flash to half of the island,” Joseph, who lives at home with his parents on Staten Island, posted in August. “ur white! Stop talking like ur a shwoog.”

In November 2011, Joseph laid into rapper Flo Rida after the performer sampled the song “Levels,” by Tim Bergling, in his own tune “Good Feeling.”

“This dumb shwoogie Flo-rida should be shanked for what he did to levels,” he opined.

In January 2012, Joseph and a buddy traded tweets about Jews.

“I saw a sick jew walking on bloomingdale and thought of you,” Joseph posted to the pal, who uses the twitter name @breezyy.

In November 2011, the duo had an exchange after @breezyy posted a photo of a Hasidic Jew near a basketball court where kids were playing and wrote: “This no good Hebrewwww crepin on the kidssssss.”

Joseph replied, “I like jews about as much as hitler #toofar? NOPE.”

The FDNY progeny openly admits on Twitter that his remarks have gotten him in hot water in the past.

Last March, Joseph, who plays in a local baseball league, disclosed that he had been suspended for five games because of a Twitter post.

“1 game down 4 more to go,” he tweeted on March 16, 2012.

When one of his friends asked what he’d done, Cassano replied, “got suspended for a tweet #suspendedchild.”

Young Cassano also displays a vulgar attitude toward women.

“I love boob jobs . . . I wish every girl in America were forced to get one once they turn 18,” he wrote in November.

He added, “I’ll vote in the presidential election when a candidates main purpose is to make breast enhancement surgery free to all who want it.”